Dig a trench for mowing strip

Need someone to dig a trench approximately 12 meters long for mowing strip on a sloping site. Trench needs to be 300 wide and min 350 mm deep to stop Kikuyu grass invading garden beds. It should be relatively easy as I already created an edge but now want to move the edge out. We have clay soil so it's sticky especially with all the rain we had in the last few weeks. Soil removed needs to be moved another 10 m using wheelbarrow. If you have expertise in creating concrete mowing strip then it will be a further job.